When to stop draw filing the barrel.

[RaiderSix]

I am draw filing my first barrel (.40 cal Rice swamped SMR) and want to make sure I am not going too far. I’m using Jim’s video as a guide and am able to get into a nice flow with the file. The “problem” (maybe it’s totally normal) is that it’s taking a while to get the machine marks out of the centerline of the flat. The outside edges of the flat are coming clean first, with the centerline taking considerably more work. I ended up using a Sharpie to help guide me. I’m guessing that it is just slightly hollow ground, and that I should keep going until those machine marks in the centerline are gone. Either that or I am rocking the file and not knowing it.

[Bill Raby]

You have to get those tools marks out of the center. My guess is that you are rocking the file. Barrel profiles are cut on a  horizontal mill. You are not going to get any hollow ground from that. Every barrel that I have worked on was flat across the flats.

[45-110]

Just finished up a old NOS Sharon barrel, and it too was hollow ground in the center. Lots of metal removal to get center trough removed and everything flat and clean.
kw

[RaiderSix]

I put a straight edge on one of the untouched (by me) flats along the barrel’s length and confirmed my theory. I only checked a few spots, and one spot even had a bit of a hump. I was using a big old 10” (pardon my French) bastard file that was a little clumsy and I guess a little rougher than ideal. So I went ahead and placed an order for some 8” Bahco files in the proper “grit.” 😬 It was hard to find a singular file, since they seem to want to sell them by the bushel. I’m going to put the barrel on pause until the files come in, and turn my attention back to finishing the stock.

[JPK]

How can you inlet the barrel with out draw filing it first? Seems it wouldn’t fit well or set down to the bottom if drawn after inletting.

[rich pierce]

How can you inlet the barrel with out draw filing it first? Seems it wouldn’t fit well or set down to the bottom if drawn after inletting.

A couple thousandths of an inch at most are lost when draw filing. Sometimes it cannot be measured.

[Stoner creek]

I like inletting the barrel snug and draw filing after its inlet. Always seems to fit just right afterwards.
W

[RAT]

I draw file and polish to a 150 grit before inletting. I use the file Brownells sells specifically for draw filing barrels. Since it's short and wide it stays flat without rocking. It removes metal fairly quickly. I polish using sandpaper taped to popsicle sticks with double sided tape.

A few people have been trying to convince me to stop at filing, and not sand it at all. The filed finish being more authentic. Like a lot of us, I guess I'm addicted to the use of sandpaper and a finer finish.

[flatsguide]

Those same “few people” also use that excuse for sloppy work including leaving tool marks. Below is an idea for your draw filing
https://americanlongrifles.org/forum/index.php?topic=63682.0
Flame suit on
Cheers Richard

[RaiderSix]

Nice barrel spinner. Looks like it would save a lot of vice clamping and unclamping.

[Goo]

In my experience finishing stones do a better job and when used properly actually provide a nicer finish.

[Bob Roller]

On the few I have built I used a 10 inch lathe file.Short,thick and rigid and How does a concave radius occur? I used Bill Large barrels and never noticed such a thing.The file was always new and sharp.
Bob Roller

[flatsguide]

Goo, after draw filing I do use stones to get the finish I want..
Bob has the right idea of using a lathe file, the teeth are deep to minimize pining and and angle much more sharply than a regular file. Bob, I think if there is a concave radius on the the not so flat flats the mill is not in tram therefore cutting a concave radius.
Richard

[Bob Roller]

The only "Milled"barrels I have seen are a few pistol barrels done on a vertical mill in my shop** many
years ago.ALL barrels from Bill Large's shop were done on a planer and Bill had 2 of them'.
** a machinst friend used my mill because an anti gun foreman told him he could do NO GUN parts for
any kind of guns.I had one request I did turn down and that was to help reactivate a VERY FAST firing German WW2
bring back.I told him I and my tools were dedicated to to muzzle loaders and single shot guns only and his idea
of reactivating the gun he has was asking for trouble in capital letters.
Bob Roller

[Jim Kibler]

Drawfiling takes some time to learn and gain control.  After this, it really is a great process that creates a remarkable finish without too much work at all.  I often go from drawfiling straight to barrel finishing.

A few notes...

I like to use about an 8" file.   
Check the file for straightness by sighting down it's length.  Assuming it is straight is a bad approach.  If it is bent, your best to put the convex side down.
Hold the file close to the barrel to maintain maximum control.
I think I show this whole process in a video that you can check out.

As far as barrels go, we side mill the flats so they are very flat.  Cutters can wear a touch but the amount that the flats vary from being flat is very minute.  Some manufacturers use a facemill to cut the flats.  With a swamped or tapered barrel, this creates a very small hollow in the cut.

As you demonstrate, light can show deviation, but it is extremenly sensitive.  A thousandths or two can look like a mile, so it's good to keep this in mind.

Jim

[Bob Roller]

Maybe a helpful hint could be,Ger some Dykem Blue and paint each flat before starting the draw filing and the irregularities will stand out like a goose egg in a coal bucket ;
Bob Roller

[davec2]

A while back I did a "draw filing experiment" on a barrel that came with one of Jim's earlier colonial rifle kits I assembled.  Here is a summation....

I had an hour today and thought I would try and get the barrel draw filed.  Now right out of the crate, the barrel had the expected tool marks full length along all of the flats....not really deep but significant enough that I thought I might not be able to get all the draw filing done in the hour I had.  In addition, there was some discontinuity in the surfaces near the waist where the barrel was moved in the machine to complete the milling of each flat.  Again, no criticism here, I just thought it would take a little more time in those areas to get the surface discrepancy filed out.

Just for fun, I took out my phone and opened the stop watch function.  I hit the button on the stop watch and started in on one flat.  It went really well and when I finished I reached over and hit the "stop" button.....5 minutes and 35 seconds.  I timed each of the next four flats.....all less than 6 minutes.  All five primary flats draw filed in less than 30 minutes.  It went so quickly and well, I had time to finish up all eight flats...just for kicks. 

One last point of interest....as I was sweeping up the steel filings on the bench and floor I looked over and saw a gram scale on my bench that I use for making detonators for explosive charges.  I weighed the steel filings to see how much metal I had removed......9.8 grams.  So just in case anyone else out there was wondering how much metal you are taking off draw filing a barrel, there is is......right about 1.1 grams for each flat on a 43" barrel.

I did convert the 1.1 grams of steel removed per flat to a thickness.  Assuming an average flat width of 0.4", a barrel length of 43", and a density for mild steel of 0.2904 lbs / in^3, the 1.1 grams of steel removed per flat to clean up the surface equates to 0.00053" in thickness.  So, on average, the removal of a half a thousandth of an inch of material results in a smooth file finish with no remaining tool marks.


And here is the complete link.........

https://americanlongrifles.org/forum/index.php?topic=57140.0

[justinp61]

I used a straight 7/8" Rice barrel on my .40 build earlier this year. The flats were like the OP's, all over the place, On one the milling marks looked like they changed directions when they got to the end. I started out with large (18-20") coarse Nicholson files and worked my way down to finer files, then to 220 grit sandpaper. I also filed length wise using the full length of the file. This showed many low or high spots on the barrel. Even after all the filing the barrel still measures on the heavy side of 7/8". Having never draw filed a barrel I probably went about it the wrong way, it came out well though.

[Bob Roller]

Caution,IF the rear sight dove tail vanishes after the draw filing,something is OFF the tracks.
Bob Roller

[rich pierce]

After about 20 minutes is when I usually quit draw filing. 

There are so many finishes folks strive for that there is no one answer that fits all. Unless one dilutes any browning solution and goes slow there’s a chance of ending up with a more coarse, rough appearance than after draw filing. Sometimes that is intentional.

I don’t draw file the bottom 3 flats on guns for myself. I ask customers if they want it like originals or contemporary guns where hidden areas are treated as though visible.

[ettoreR]

I am draw filing my first barrel (.40 cal Rice swamped SMR) and want to make sure I am not going too far. I’m using Jim’s video as a guide and am able to get into a nice flow with the file. The “problem” (maybe it’s totally normal) is that it’s taking a while to get the machine marks out of the centerline of the flat. The outside edges of the flat are coming clean first, with the centerline taking considerably more work. I ended up using a Sharpie to help guide me. I’m guessing that it is just slightly hollow ground, and that I should keep going until those machine marks in the centerline are gone. Either that or I am rocking the file and not knowing it.

Draw file untill the surface is somewhat bright, grt most tool marks out, all of you're picky. Finish is off with some 600 grit sandpaper and the. Some maroon scotchbright, which will even the finish out. No gun is perfect but you'd do well tomake it look nice, in a workman type manner. Small imperfections add character and are realistic for what we are trying to produce.